How do I make an environment sphere thing? (like Blender's preview)
It is quite easy. Just have a glossy material with very little or no roughness.
There you are, done!


Really? But, where is the texture?
The reflections are not part of the texture, the reflections are determined by the environment that surrounds the object, just like in a mirror.
If you add an HDR image as your world enviroment texture it will be reflected on the surface.

More info on this link:
Why does an object with a glossy shader render in black?